Blue emission from silk fibroin-Yb3+/Tm3+:YAG films by up-conversion

Developing systems that can stop counterfeiting is crucial. In this sense, luminescent markers are a good strategy because the label is only visible under special conditions. In this scenario, the up-conversion emission mechanism is an example of cutting-edge knowledge, especially the blue emission, which requires at least three photons to occur. Here, we have prepared a new material based on silk fibroin and inorganic particles doped with Yb3+/ Tm3+ ions and investigated the blue up-conversion process in it. This association of particles and silk fibroin allowed us to explore the exceptional properties of this protein allied with the multifunctionality of lanthanides: the resulting biodegradable, self-supported film emits in the blue region and can be applied as an anti-counterfeiting device, surface coating, or even an ink for 3D printers. (AU)